Viscose-cellulose ether solution



Patented June 13, 1939 PATENT OFFICE aisam vrsoosa-orgmumsa n'rnsn summon Robert W. Maxwell, Wilmington, Del., assignor to E. L du Pont de Nemours Comp Wilmington. Del., a corporation oi Delaware No Drawing. Ap

cation January 8, 1938,

pl! v Serial No. mam

Claims. (01. zoo-m) This invention relates to regenerated cellulose (rayon), and more particularly to a regenerated cellulose which is superior to the heretofore known regenerated celluloses in dyeing properties a deformation properties, and moisture-proof filmretaining properties.

Ordinary regenerated cellulose film, which has been coated with a wax composition to render it moisture-proof, rapidly (in an hour or two) 10- loses its eilectiveness in the presence of water.

The loosening and detachment oi the wax composition layer which results irom contact with water precludes the use oi such a material in many fields. Numerous efforts to overcome this property of the regenerated cellulose have been made. These included, inter alia, the use oi other (than wax) coating compositions and the use of intermediate films to anchor the wax coat to the regenerated cellulose, which would increase undesirably the cost oi the material.

It is also known that regenerated cellulose threads (filaments) reflect with a sort oi magniiying ellect small variations in regenerating conditions in such a way that large variations in dyeing characteristics result. In addition, regenerated cellulose yarns do not dye as well as is desired with certain types of dyes, for example, direct dyes. This disadvantage (apparently a lack oi afilnity for important classes of dyes) has been the incentive for much research, but up to the present time neither of these undesirable properties has been satisfactorily overcome.

It is also known that regenerated cellulose filaments and films possess the undesirable property 3 of expanding and contracting considerably with changes in humidity. This disadvantage has been a source of worry to the manufacturers and users of cellulose films, and has handicapped them for many years. Much time and money have been spent in efi'orts to produce a regenerated cellulose film devoid of this drawback.

This invention had for an object the preparation of a regenerated cellulose having superior dyeing characteristics. Other objects were the preparation oi a regenerated cellulose having superior adherence to moisture-proof coatings, having improved resistance to deformation and having both good wet strength and desirable dyeing properties. Still further objects were the 5 preparation of new and improved viscoses and regenerating procedures and products. A general advance in the art and other objects which will appear hereinafter are also contemplated.

It has now been found that all the aforemen- 55 tioned obstacles to the use of regenerated cellulose can be overcome by the simple expedient of incorporating in the viscose prior to regeneration a minor proportion oi a low substituted cellulose ether which is soluble in dilute aqueous caustic soda. The resulting modified regenerated cellu- 5 lose does not have the disadvantages described above.

It has previously been proposed that equal parts of viscose and caustic alkali solutions of cellulose ethers be spun into fibers. There seems to be 10 no particular advantage in such a process. Such mixtures give coagulated products having a wet strength too low to be spun by prevailing commercial methods. Even, when in order to get threads for experimental purposes, commercially l5 impractical procedures are employed, it is almost impossible to spin and handle the filaments because they stick together on the bobbin. In addition, the dried filaments 01' such mixtures are harsh and unpleasant to touch. 20

From the following description and specific examples, in which are disclosed certain embodiments of the invention as well as details of what is believed to be the best mode for carrying out the invention, it will be apparent how the fore- 25 going objects and related ends are accomplished. The quantities are given in parts by weight throughout the application.

Exam is I Twenty-five (25) parts of a 6% solution oi. a water soluble glycol cellulose in 7% aqueous caustic soda prepared as described in Example XXII, were mixed with 75 parts 01 a viscose containing 6% cellulose and 6% sodium hydroxide. After ripening for 48 hours at 25 C. the mixture was cast into a transparent film in the usual way, and after drying, was coated with a moisture-proofing lacquer such as that described in United States Patent 1,737,187 issued November 26, 1929, to Charch. It was necessary to soak the coated film in water at 25 C. for six days before the lacquer coating could be detached by rubbing gently between the fingers.

A film of regenerated cellulose prepared from 45 the same viscose in the same manner and coated with the same composition in the same manner could be separated from its lacquer coating with the same treatment after soaking in water at 25 C. for about two hours. 50

l The glycol cellulose contained about one glycol group per glucose unit of the cellulose. As a result'the average composition of the celluloseglycol cellulose mixture was one glycol group for every low glucose units present (i. e., both in the cellulose and in the glycol cellulose). The films of the cellulose-glycol cellulose mixture were very much stronger when wet than films of glycol cellulose containing .25 glycol groups per glucose unit which had been coagulated from an alkali solution of the glycol cellulose. They were also very much stronger when wet than films of glycol cellulose containing .25 glycol groups per glucose unit which had been regenerated from a viscoselike solution of a xanthated glycol cellulose.

Example II Five parts of a 6% solution of a water soluble glycol cellulose in 7% aqueous caustic soda prepared as described in Example xxn were mixed with 95 parts of viscose containing 7% cellulose and 6% sodium hydroxide. After suitable ripeningthemixturewascastintofilmsina sulfuric acid sodium suliate bath by a thin film on a glass plate and dipping it into the warm precipitating bath. The films were washed acid free with water, steeped in a 4% aqueous solution of glycerin and dried. The film after drying was coated with a moisture-proofing lacquer having a nitrocellulose base. After soaking in water at 25 C. for two days the moisture-proofing layer was still tightly bound to the base.

This product (moisture-proofed) has, after extensive tests, been found particularly suitable for -n'i11k bottle hoods.

The ratio of wet to dry strength of filaments made from the cellulose-glycol cellulose solution of this example was substantially the same as that of filaments made from the same viscose to which no glycol cellulose solution had been added. namely, 0.474. The average number of glycol groups present per glucose unit of cellulose plus glycol cellulose was 0.05. Filaments regenerated from a xanthated glycol cellulose containing 0.06 glycol groups per glucose unit had a ratio of wet to dry strength which was 0.396.

The aforementioned cellulose-glycol cellulose filaments showed a considerably greater afilnity for Pontamine Sky Blue 6 13K (a direct dye, C. I. 518) than the aforementioned regenerated cellu lose filaments.

Emmple III One (1) part of a 6% solution of a water soluble glycol cellulose in 7% aqueous caustic soda prepared as described in Example XXII was mixed with 99 parts of viscose containing 7% cellulose and 6% sodium hydroxide. After suitable ripening the mixture was cast into films. These showed a markedly increased aifinity for substantive dyestufis compared with films made from the same viscose without modification.

Example IV Ten (10) parts oi a 7% solution in water of a water soluble sodium cellulose glycolate (containing 0.5 glycolic acid ether group per glucose unit of the cellulose) were mixed with 90 parts of a viscose solution containing 7% cellulose and 6% sodium hydroxide. The resulting solution was cast into films in the usual way and was then coated with a moisture-proofing lacquer. It was necessary to soak the resulting film in water for two days before the lacquer coating could be detached by rubbing gently with the fingers.

The wet strength of filaments prepared by the xanthation and regeneration of a cellulose slycolic acid containing the same average content of glycoiic acid radicals as the cellulose-cellulose glycoiic acid mixture was more than 10% lower.

The cellulose-cellulose glycolic acid mixture "filaments had an increased afiinity for basic dyes same when compared with filaments from the viscose which had not been modified.

trample V Twenty-five parts of a 7% solution in water of a water soluble sodium cellulose glycolate (containing 0.5 glycoiic acid ether groups per Glucose unit of the cellulose) were mixed wlth75 Parts of a viscose solution containing 7% cellulose and 6% sodium hydroxide. The resulting solution was cast into films. After moistureproofing in the same way as that described in Example IV, a product was obtained which could u Twenty-five (25) parts of a 7% solution of a water insoluble room temperature alkali-soluble glycol cellulose in 7% aqueous caustic soda described in Example XXIII were mixed with 75 parts of a viscose containing 7% cellulose and 6% sodium hydroxide. The resulting solution was ripened and cast into films. Alter moistureproofing with a composition based on nitrocellulose, a product was obtained which exhibited a marked resistance to separation of the baselayer and lacquer coating when immersed in water.

Filaments of the product spun at low tensions were found to a wet strength equivalent to about 80% of filaments spun from the same viscose under the same conditions, whereas filaments regenerated from a xanthated glycol cellulose of approximately the same storage degree of substitution (0.10 mol of glycol radical per glucose unit) under corresponding conditions a wet strength of only of that of the viscose filaments.

Example VII Two (2) parts of a. 7% solution of a water insoluble room temperature alkali-soluble glycol cellulose in 7% aqueous caustic soda described in Example XXIII were mixed with 98 parts of a viscose containing 7% cellulose and 6% sodium hydroxide. The resulting solution was spun into filaments using a sulfuric acid bath of greater than 40% sulfuric acid strength. The resulting filaments possessed a wet strength substantially equivalent to that of filaments prepared in the same manner from the same viscose, but the ailinity for direct dyes such as Pontamine Sky Blue 63X (0. I. 518) was markedly increased.

Example VIII Twenty-five (25) parts of a 7% solution of a water insoluble glycol cellulose not dissolved by dilute caustic soda at room temperature but dissolved therein by chilling, in 7% aqueous caustic soda' prepared as. described in Example xxrv, were These films ai'ter coating with a, moisture-proofing also,

suliat'e-rsuliuricacid bath in the way well known in the viscose art. The wet'film-was almost strong as that made trom viscose. Films regeneratedtrom this mixturewere dye in the same direct dye both as filaments oi regenerated cellulose prepared from the viscose -.alone by the same regeneration procedure. The

film containing the ether dyed much more deeply than did the regenerated cellulose film. f

lcamrle x water insoluble glycol cellulose not dissolved by dilute caustic soda at room temperature but, dissolved therein by chilling, in 1% aqueous caustic soda prepared as described in Example XXIV, were mixed with '15 parts of a viscose containing 1% cellulose and 6% sodium hydroxide. The viscose-like solution was cast into films in the usual way and was then coated with a lacguer basedon ethyl cellulose. The coated film could be immersed in water for several days without the lacquer layer becoming suificiently loosened to become easily detached by rubbing gently between the dimers. we

Example XI One (1) part of a 1% solution of a water insol- Example x11" One (1) part oia-'1% solution of a water insoluble glycol cellulose not dissolved by dilute caustic soda at roomtemperature but dissolved therein by chilling, in 1% aqueous caustic soda prepared as described in Example XXIV, was mixed with v 99 parts oi a viscose containing 1% cellulose and 6% sodium hydroxide. The resulting viscose-like product was spun into filaments into a bath of the usual composition containing sodium sulfate, sulfuric acid, glucose and zinc'suliate, in the usual manner. The filaments thus obtained showed a markedly greater afiinity for direct dyes than did the viscose rayon prepared from the original viscosein the same spinning bath under the same conditions. The dyeing oi the cellulose-cellulose ether filaments was unusually level.

Example XIII .Twenty-five parts of a 1% solution of water insoluble sodium cellulose glycolate not dissolved by dilute caustic soda solution at room temperature but dissolved therein upon cooling, in 1% sodium hydroxide prepared as described in Example XXV, were mixed with '15 parts oi viscose containing 1% cellulose and 6% sodium hydroxide. Alter thorough minng, the viscoselike solutionwas filtered and cast into films.

composition in accordance with the disclosure in United States Patent No. 1,137,187, gave a product which could be soaked in water at least ten times as long as films regenerated irom the same viscose under the same conditions before the moisture-proofing film could be removed by rubbing gently between the fingers. The cellulosecellulose ether films exhibited a strong aiilnity for basic dyes. Thewet strength oi the films was well within a commercially useful range, although it was somewhat lower than that 0! regenerated cellulose film made irom the same viscose under similar conditions.

Treatment of the cellulose-cellulose ether films with solutions of salts which give precipitates with solutions of water soluble sodium cellulose glycolate, such; as potassium aluminum sulfate, Twenty-five (25) parts or a 1%solution oi a resulted in products which were more water repellent. than the starting The alum treated film burned with considerable diflicuity as compared with ordinary regenerated cellulose.

Eaample XIV Twenty-five. (25) parts of a 1% solution of sodium cellulose giycolate not dissolved by dilute caustic soda solution at room temperature but dissolved therein upon cooling, in 1% sodium hydroxide prepared as described in Example XXV,

were mixed with '15 parts of viscose containing be soaked in water at least several times as long as films regenerated from the same viscose under the same condltionsbeiore the moisture-proofing film could be removed by rubbing gently between the fingers. The cellulose-cellulose ether films were somewhat less resistant to loosening of their moisture-proof coating bywater than the product 01 Example XIII. The dyeing afiinity was much the same as the product of Example XIII, but the wet strength was much improved thereover.

Filaments spun from the same viscose-like mixture at low tension possessed a wet strength equal to approximately 80% of that of filaments spun from the same viscose in the same way. In contrast, the filaments spun from a xanthated cellulose giycolic acid containing the same aver- .age number of glycoiic acid radicals per glucose unit as did the cellulose-cellulose glycolic acid mixture (based on the total number of glucose units in the mixture) possessed a wet strength approximately equal to only 60% of the regenerated cellulose filaments.

Example XV solution was filtered, and films and filaments prepared therefrom in the usual manner. The regenerated products had an increased amnity for basic dyestufis such as Du Pont Methyl Violet NE (0. I. 680) Example XVI Two (2) parts 01 d 7% solution'of a. water insoluble sodium cellulose glycolate which is dissolved by dilute caustic soda at room temperature (prepared according to Example m1), in-7% sodium hydroxide, were mixed with 90 parts 01' a viscose solution containing 7% precipitatable cellulose. The resulting viscose-like body was cast into film being precipitated in a bath composed oi 10% sulfuric acid and 20% sodium sulfate and 70% water.

The films were washed and'dried in the usual manner. Dye tests comparing these films with films from the same viscose prepared in the same manner showed that with basic dyes such as Du Pont Methyl Violet NE (0. I. 600) the film containing the small amount of cellulose ether dyed approximately 50% stronger. The wet strength of the cellulose-cellulose ether films wasvery close to that of the regenerated cellulose films.

Example XVII Twenty (20) parts of a 5% solution of a water insoluble room temperature dilute caustic soda soluble methyl cellulose prepared according to Example XXVII in 8% aqueous sodium hydroxide, were mixed with 80 parts of a viscose containlng 7% cellulose and 7% sodium hydroxide. The solution was ripened for 40 hours at 25 C. and then cast into films, using a bath containing 12% sulfuric acid, 20% sodium sulfate and 68% water in the usual manner. The resulting films possessed an excellent wet strength and were dyed considerably deeper with substantive dyes than the corresponding regenerated cellulose. The afilnity for moisture-proofing lacquer in the presence of water was many times as great as ordinary regenerated cellulose.

Example XVIII One-half ,5) part of a 5% solution of a water insoluble room temperature dilute caustic soda soluble methyl cellulose prepared according to Example XXVI! in 8% aqueous sodium hydroxide, was mixed with 99.5 parts of a viscose containing 7% cellulose and 7% sodium hydroxide. The solution was ripened for 24 hours at 25" C. and spun into a bath composed of sodium sulfate, glucose, sulfuric acid, zinc sulfate and water, using a series of guide arrangements adapted to give considerable tension on the regenerated filaments during the regeneration step. The modified regenerated cellulose filaments dyed approximately the same with direct dyes as filaments spun from the corresponding unmodified viscose at lower tension,

Example XIX- Twenty-five (25) parts of a 1% solution of a water insoluble methyl cellulose not dissolved by dilute caustic soda at room temperature but dissolved therein by chilling to temperatures approximating the freezing point, prepared according to Example XXVIII in 7% aqueous sodium hydroxide, were mixed with 75 parts of viscose containing 7% precipitatable cellulose and 7% sodium hydroxide. The resulting solution was ripened and spun into filaments in the wellknown manner. 0!: dyeing with direct dyes such as Pontamine Sky Blue GBX (C. I. 518) there was obtained a product with a depth of color about twice that obtained from the corresponding viscose rayon.

Example XX Twenty-five (25) parts ofa 7% solutionof a water insoluble methyl cellulose not dissolved by dilute caustic soda' at room temperature but dissolved therein by chilling to temperatures approximating the freezing point, prepared according to Example XxVIII-in 7% aqueous sodium hydroxide, were mixed with 75 parts of viscose containing 7% precipitatable cellulom and 7% sodium hydroxide. Upon regenerating the mixture at a sodium chloride index of 2, films were obtained of excellent wet strength. They showed a greater amnlty for direct dyes than the corresponding regenerated cellulose. After drying some of the cellulose-cellulose ether films were coated with a nitrocellulose base moisture-prooflng lacquer. It required more than three days soaking in water to loosen the moisture-proof layer sufliclently to enable it to be detached by rubbing gently between the fingers.

Filaments spun from the viscose-like solution possessed a wet strength only slightly inferior to that of yarn spun from unmodified viscose. Filaments spun from a xanthated methyl cellulose containing the same proportion of methyl groups as the viscose-methyl cellulose mixture solution (based upon the sum of the glucose units present in the methyl cellulose and the cellulose) possessed a wet strength of only about 80% of that of the viscose rayon. Comparable conditions were employed in xanthating the regenerating the methyl cellulose referred to.

Example XXI One (1) part of a 7% solution of a water insoluble methyl cellulose not dissolved by dilute caustic soda at room temperature but dissolved therein by chilling to temperatures approximating the freezing point, prepared according to Example KXVIII in 7% aqueous sodium hydroxide, was mixed with 99 parts of viscose containing 7% precipitatable cellulose and 7% sodium hydroxide.

The viscose was ripened and then spun into filaments, using one of the common coagulating baths containing sulfuric acid, glucose, sodium sulfate, and zinc sulfate. The filaments gave a markedly increased ailinity for Pontamine Sky Blue sax (C. I. 511i), a direct dye, when compared with the corresponding'viscose-rayon.

Example XXII One hundred andsixty (100) parts of sulfite cellulose were steeped in 2000 parts of 18% sodium hydroxide. After one hour at 25 C. the alkali cellulose was pressed to 400 parts and then shredded for two hours at C. It was then placed in a baratte (tumbling device) and provided with a means of vaporizing ethylene oxide into the interior. Eighty-eight (88) parts of ethylene oxide were allowed to vaporize into the apparatus at 20 C. over a period of twelve hours. The resulting product was aged for 24 hours at 25 C. A test sample showed the aged product to be water soluble. An aqueous stock solution containing 6% of the glycol cellulose and 7% sodium hydroxide was then prepared.

Example XXIII Example XXIV One hundred (100) parts of. sulfite wood pulp were steeped in 1600 parts of 18% caustic for one hour at 35" C. The alkali cellulose was then pressed to 400 parts, shredded roitwo hours at 30" 0., treated with ii parts oi. ethylene oxide at 25 C. for two hours and then .aged for twenty hours at 30 C. to reduce viscosity. The resulting glycol cellulose was insoluble in dilute caustic soda at room temperature. It was formed into a 7% stock soluti n in 7% aqueous sodium hydroxide beiore coolin to 6 C. as soon as the material had again acquired room temperature (25'' C.) a perfectly stable solution resulted.

This ether is an example of those low substituted cellulose ethers which are not initially soluble (dissolved by) dilute (6%) aqueous caus-' tic soda at room temperature but which are dissolved therein by cooling to temperatures nearer the freezing point of the mixture.

Example XXV One hundred and sixty (180). parts or ovendried suliite pulp were steeped in 1600 parts of 20% caustic-for two hours at 25C. The alkali 'ceilulose was pressed to 400 parts,.placed in a shredder with 40 parts of sodium chloroacetate and shredded for three hours. The reaction mixture wasthen' removed from the shredder and aged for 40 hours at 25 C. r The resulting cellulose glycolic acid which was not dissolved indilute caustic soda ,-(4%',-1o%) solutions at room temperature was made into a 7% solution in 1% sodium hydroxide by cooling amixture of the cellulose glycolic acid and sodium hydroxide in proper proportions to -8C.'.

Example xxvr Example XXVI! One hundred and sixty (160) parts of air dried suliite cellulose were steeped in 18% caustic I; one hour at 25 C. and'then pressed to 400 P 8-. with 134 parts of dimethyl sulfate at room tem perature. After' shreddingv for three hours the product was removedandpermitted to age for 24 hours at,25 C. It was then water insoluble but dissolved in dilute aqueous caustic soda at room temperature. The product was washed with warm water until free of caustic, aiter which it wasdissolved to give a solution containing 5% cellulose and 8% sodium hydroxide. It was flitered through cotton batting.

Erample xxvm One hundred and sixty (160) parts of sulflte cellulose were steeped in 18% caustic for one hour at 25' c., pressed to 480 parts, mixed in a shredder with 35 parts of dimethyl sulfateat 20 0., removed and aged for 24 hours at 25 C. The'product was purified by washing with hot. water until free ofalkall, then dissolved to give an aqueous solution containing 7% cellulose and 7% sodium hydroxide by cooling to 5 C. Tests showed this methyl cellulose to be insoluble in water and dilute aqueous caustic soda at room temperature but dissolved ill'dillite aque- This alkali cellulose was then treated ouscausticsodabychiliingtoabove and-near. the freezing point. Before the cooling referred to above in the preparation oi'the solution, the

product was undissolved by the causticasoda. Aftercoolingitgaveasolutionstable at ,0. 7 a

Theceliulo'se xanthate may be madebya'ny ,of'the methods known in the It makes little dliierence what sort of cellulose the ,viscose'ismadefrom oiongasitisoneofthe.

types satistactory for the preparation of viscose suitable tor the manufacture of mm and illsments by present day commercial practice. A viscose of about 40 poises viscosity in 1% solution'in 7% sodium hydroxide at 25' C. is preferred, although other viscosities and concentra- Any cellulose ether which is soluble in alkali may be used to modify the viscose. The invention is most satisfactorily operated with those cellulose ethers which are not dissolved by water or caustic soda at room temperature but which are dissolved in dilute aqueous caustic soda upon cooling to below 0 C. In. general, cellulose ethers soluble in caustic alkali and soiublein water. cellulose ethers insoluble in water but dissolved by caustic alkali at room temperature.and at low temperatures approximating the freezing point of the mixture, and the cellulose ethers which are not dissolved by water or caustic soda at room temperature but which are dissolved under suitable conditions in dilute aqueous caustic soda chilling to above and near the freezing point, may be used.

Among the caustic alkali soluble ethers suitable for modifying the regenerated cellulose, special mention may be made of methyl cellulose, ethyl celiuloseglycol cellulose, propylene glycol cellulose, isobutylene glycol cellulose, cycohexene gycol cellulose, giyceryl cellulose, cellulose' gycoiic acid, and cellulose propionic acid. Mixedceliuiose ethers such as methyl cellulose glycolic acid and methyl glycol cellulose.v operate satisfactorily, providing the required solubility is present.

In general 25% of any of the alkali soluble ethers is sumcient to give the desired eifect. Quantities appreciably greater than 25% conter undesirable properties on the y rn, such as harshness, low wet strength. etc. In most instances lower proportions can be toleratedsafely. Ethers soluble in water are ordinarily used in limited amounts because larger quantities tend to lower the wet strength of the product to a de-, gree which is undesirable for many purposes. The cellulose ethers which are dissolved by causrtic alkali at room temperature and at low temperatures but which are not dissolved by water, are less prone to cause trouble. Thelower substituted ethers, particularly the allryl celluloses, which are dissolved by dilute aqueous caustic soda at low temperatures approximating the freezing point but are not dissolved thereby at room temperature, are the most satisfactory or all for this purpose, and they constitute a preferred embodiment of the invention.

For most purposes, such as to eifect modification of dyeing characteristics, 5% oi the alkali soluble ether is a sufilcient-quantity of modifying agent, and employment of amounts up to 5% is the preferred range. This amount is large enough to give a significant eifect. but small enough to leave the physical properties of the modified regenerated products "only slightly shamed compared with those of regenerated cellulose alone. For the purposes of dyeing control, the utilization of less than 1% of modifying agent is especially desirable since. this gives a marked e'ifect on dyeing characteristics with practically no change in the usual physical characteristics. The products of this invention are so sensitive to dyeing that percentages of cellulose ether as low as .1% and less in the resenerated material in many cases serve to correct variations in production procedures and raw materials. 1

The eiiect of the caustic alkali soluble ethers upon the properties of articles regenerated in accordance with this invention such as resistance to changes in size (dimension) with changes in humidity or afilnity for moisture-proofing lacquer, is about the same, regardless of the degree of the substitution of the ether. A glycol cellulose soluble in water and present in the viscose in a quantity equal to 15% of the total precipitatable matter in thecellulose ether-viscose mixture has about the same effect on the aforementioned resistance to deformation as 16% of a glycol celluidea which is dissolved only by dilute aqueous caustic soda at about the freezing point. The same relationship appears to hold for the other ethers. I

The cellulose ethers used in the hereinbefore described processes are (in general) prepared by treating an alkali cellulose with an 'etherifying agent or any of the other practical cellulose etherification methods. Cellulose glycolic acids whose sodium salts are soluble in water or insoluble in water and dissolved by caustic alkali at room temperature, are well-known, especially in the patent literature. The same is true of methyl cellulose soluble in 6% caustic soda at room temperature but insoluble in water. Cellulose glycolic acids which are not dissolved .(in the form of the sodium salt) by caustic sodaat room temperaturebut which are dissolved therein upon cooling to near the freezing point thereof, are described in United States Patent No. 2,060,058. Methyl celluloses which are insoluble in water and caustic soda at room temperature but which dissolve in dilute aqueous caustic soda upon cooling to near the freezing point. are described in United States patent application Serial No. 180,964 filed December 21, 1937-. The preparation of such glycol celluloses is described in United States Patent No. 1,941,278.

The viscose-cellulose ether mixture may be made in any desirable or convenient manner. Mention may be made of such procedures as the addition of the cellulose ether to the cellulose xanthate followed by solution of the mixture of the two (accompanied by cooling if necessary), the addition of the undissolved ether to a viscose.

and the addition of a solution of the cellulose.

ether in caustic alkali to the viscose. In some cases it may be desirable to dissolve the cellulose ether in a solution of caustic alkali and then to dissolve thexanthate in the resultant, In general any procedure which results in a. homogeneous mixture (solution) of the cellulose xanthate and the cellulose ether is satisfactory. Vigorous agitation is often necessary to accomplish solution, since the salt present in the viscose or cellulose xanthate sometimes exerts a salting-out action on the cellulose ether. This is particularly true when the cellulose ether is of a very low substituted variety. The ethers may be added as solutions of their crude reaction mixtures if found convenient.

'lhe viscose-cellulose ether mixtures are very s. Sulfuric acid molar) plus magnesium V sulfate (0.1 molar).

4. Sulfuric acid (0.5 molar) plus ammonium sulfate (0.5 molar).

5. Sulfuric acid (0.5 molar) plus sodium sulfate (0.5 molar).

In the spinning of high tenacity yarns, high sulfuric acid concentration baths (above 40%) are particularly applicable.

The regeneration may involve spinning into acid baths of high concentration or' into baths provided with special guide arrangements designed and adapted to apply tension to the filaments, as will be clear from the specific examples.

In purifying the regenerated products the usual regenerated cellulose purification methods ordinar ily sufilce. Where cellulose glycolic acid has been used as the modifying cellulose ether, it is advisable to use neutral or slightly acidic washing and treating media to prevent formation of the corresponding alkali metal salt. Where such a treatment is inadvisablethe regenerated product may be given an acid treatment to coagulate (regenerate) the glycolic acid, and the same followed by second washing with water.

Delusterants or other conventional modifying agents may. be added to the viscose-cellulose ether mixture.

The dyeing characteristics. of the modified rayon of this invention may be controlled by using extremely small quantities of the cellulose ether. As is well-known, variations in the spinning conditions with ordinary viscose gives yarns having difi'erent dyeing characteristics. This disadvantage is overcome by the incorporation of a regulated proportion of an alkali soluble cellulose ether in the viscose. Correction of the differences in dye afiinity is particularly important in the case of high tenacity mm which are spun under high tension because they possess a lower aihnity for direct dyes than ordinary viscose rayon. The two types of rayon can be given substantially the same amnity for direct dyes simply by including a small proportion of an alkali soluble cellulose ether solution. For example, the incorporation of methyl cellulose in viscose from which high tenacity yarn is spun results in a product having very desirable dyeing characteristics. likewise, the difference in dyeing characteristics brought about by the use of certain types of cellulose such as cotton linters in making the viscose can be overcome.

The salt forming power of the cellulose glycolic and other oxy-acid ethers of cellulose is of considerable interest because it permits the introduction of many metallic ions into the yarn. For example, treatment of the yarn with copper salts gives a yarn containing copper. Similarly, lead, aluminum, silver, ironand other insoluble salts can be formed. Such products are of especial interest for the preparation'of fireproof fabrics. yarns resistant to mildew, etc. This property of salt formation must be taken into con- The films and filaments prepared according to this invention may be used in the same manner as present day films and filaments of regenerated cellulose, with due regard to the superior properties of the products or this invention.

It has been found possible to esteriiy the free cellulosic hydroxyl groups of the regenerated cellulose of the filaments containing a small proportion of alkali soluble ether much more readily than viscose rayon simply by,heating with carboxylic acid anhydrides with or without diluents. Water repellent yarns of excellent appearance may be prepared in this manner. In such esterification processes alkaline or acid catalysts may be used to promote the reaction, and ii'v desired the yarn may be swelled with water or other pretreatlng agents to assist in the esterlficatlom As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims;

- I claim:

1. A viscose-cellulose ether solution in which not more than 1% of the regeneratable material is a cellulose ether capable of being dissolved in caustic alkali.

2. A modified regenerated cellulose containing up to 5% of an alkali soluble cellulose ether, said.

product having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose.

3. A modified ted cellulose containing up to 5% oi a water insoluble dilute alkali soluble cellulose ether.

4. A modified regenerated cellulose containing up to 1% of a cellulose ether dissolved by dilute aqueous caustic soda at low temperatures approximating the freezing point but not dissolved thereby at room temperature, said product having greater aiiinity for direct dyes and substantially the same wet strength as unmodified regenerated 5. A viscose-cellulose ether solution in which not more than 5% of the material is a cellulose ether capable of being dissolved in caustic alkali.

6. A modified regenerated cellulose containing up to 1% of an alkali soluble cellulose ether, said product having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

7. A modified regenerated cellulose containing up to 5% of a water insoluble dilute alkali soluble cellulose glycolic acid ether, said-product having greater aiilnity for basic dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

B. A modified regenerated cellulose containin up to 1% oi a glycol cellulose ether dissolved by dilute aqueous caustic soda at low temperatures approximating the freezing point but not dissolved thereby at room temperature, having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

9, A modified regenerated cellulose containing up to 5% of a low alkyl (methyl or ethyl) cellulose ether, the said cellulose ether not being dissolved by water or aqueous caustic soda at room temperature, but which is dissolved in dilute aqueous caustic soda upon chilling to above and near the freezing point, said product having greater afllnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose.

10. A modified regenerated cellulose containing up to 5% of a low substituted glycol cellulose, said glycol cellulose being insoluble in water and soluble in aqueous caustic soda, said product having greater afiinity for direct dyes and substantiallythesame wetstrengthasunmodifledregenerated cellulose and said modified regenerated cellulose having been prepared by regenerating a cellulose xanthate-alkali soluble glycol cellulose ether solution.

ROBERT W. MAXWELL.

CERTIFICATE OF CORRECTIOII- Patent no. 2,162,l|,6o.

dune 13 1959.

ROBER'I: N. Hamil-L.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, 111163 before the word 'ehilling insert upon; line 1.1, for "gycolic" read glycolic; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.-

Signed and sealed this 1st day of August, A. D. 1959.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents.

The films and filaments prepared according to this invention may be used in the same manner as present day films and filaments of regenerated cellulose, with due regard to the superior properties of the products or this invention.

It has been found possible to esteriiy the free cellulosic hydroxyl groups of the regenerated cellulose of the filaments containing a small proportion of alkali soluble ether much more readily than viscose rayon simply by,heating with carboxylic acid anhydrides with or without diluents. Water repellent yarns of excellent appearance may be prepared in this manner. In such esterification processes alkaline or acid catalysts may be used to promote the reaction, and ii'v desired the yarn may be swelled with water or other pretreatlng agents to assist in the esterlficatlom As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims;

- I claim:

1. A viscose-cellulose ether solution in which not more than 1% of the regeneratable material is a cellulose ether capable of being dissolved in caustic alkali.

2. A modified regenerated cellulose containing up to 5% of an alkali soluble cellulose ether, said.

product having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose.

3. A modified ted cellulose containing up to 5% oi a water insoluble dilute alkali soluble cellulose ether.

4. A modified regenerated cellulose containing up to 1% of a cellulose ether dissolved by dilute aqueous caustic soda at low temperatures approximating the freezing point but not dissolved thereby at room temperature, said product having greater aiiinity for direct dyes and substantially the same wet strength as unmodified regenerated 5. A viscose-cellulose ether solution in which not more than 5% of the material is a cellulose ether capable of being dissolved in caustic alkali.

6. A modified regenerated cellulose containing up to 1% of an alkali soluble cellulose ether, said product having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

7. A modified regenerated cellulose containing up to 5% of a water insoluble dilute alkali soluble cellulose glycolic acid ether, said-product having greater aiilnity for basic dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

B. A modified regenerated cellulose containin up to 1% oi a glycol cellulose ether dissolved by dilute aqueous caustic soda at low temperatures approximating the freezing point but not dissolved thereby at room temperature, having greater afilnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose and said product having been prepared by regenerating a cellulose xanthate-alkali soluble cellulose ether solution.

9, A modified regenerated cellulose containing up to 5% of a low alkyl (methyl or ethyl) cellulose ether, the said cellulose ether not being dissolved by water or aqueous caustic soda at room temperature, but which is dissolved in dilute aqueous caustic soda upon chilling to above and near the freezing point, said product having greater afllnity for direct dyes and substantially the same wet strength as unmodified regenerated cellulose.

10. A modified regenerated cellulose containing up to 5% of a low substituted glycol cellulose, said glycol cellulose being insoluble in water and soluble in aqueous caustic soda, said product having greater afiinity for direct dyes and substantiallythesame wetstrengthasunmodifledregenerated cellulose and said modified regenerated cellulose having been prepared by regenerating a cellulose xanthate-alkali soluble glycol cellulose ether solution.

ROBERT W. MAXWELL.

CERTIFICATE OF CORRECTIOII- Patent no. 2,162,l|,6o.

dune 13 1959.

ROBER'I: N. Hamil-L.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, second column, 111163 before the word 'ehilling insert upon; line 1.1, for "gycolic" read glycolic; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.-

Signed and sealed this 1st day of August, A. D. 1959.

(Seal) Henry Van Arsdale, Acting Commissioner of Patents. 

